Image processing method, image processing program, image processing apparatus, and digital still camera using the image processing apparatus

ABSTRACT

Electronic data output from CCD is separated into a brightness component Y and color difference components Cb and Cr and an edge is extracted for each of the components. The edge amounts are calculated from the extracted edges and the component having the maximum edge amount is selected. Edge information (for example, edge gradient direction) is calculated based on the selected component having the maximum edge amount, a filter is selected based on the calculated edge information about the component having the maximum edge amount, and smoothing processing is performed for the electronic data output from the CCD based on the filter. The electronic data subjected to the smoothing processing is written into flash memory.

This is a divisional of application Ser. No. 10/162,712 filed Jun. 6,2002 now U.S. Pat. No. 7,148,924. The entire disclosure of the priorapplication, application Ser. No. 10/162,712 is hereby incorporated byreference.

The present application is based on Japanese Patent Applications Nos.2001-172611 and 2002-106930, which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an image processing method, an imageprocessing program, an image processing apparatus, and a digital stillcamera using the image processing apparatus.

2. Description of the Related Art

With an image input unit, such as a digital still camera (simply,digital camera) using image input means of CCD, etc., the image inputmeans may output not only an electric signal responsive to the amount ofreceived light, but also an unnecessary electric signal. Thisunnecessary electric signal is contained in electronic data output frompixels making up an image as noise.

Hitherto, to remove noise contained in an image, edges contained in theimage have been detected from the output electronic data and informationconcerning the detected edges has been used to determine the smoothingrange for performing image processing of noise removal, etc. Forexample, using information concerning the detected edges, in theproximity of each edge, smoothing has been performed in a narrow rangealong the edge and in the surroundings of remote pixels from the edge,smoothing has been performed in a wide range.

To detect an edge, generally, output values of electronic data outputfrom the pixels making up a matrix centering on a pixel of interest (forexample, matrix of 3×3 pixels, 5×5 pixels, etc.,) are used. Theelectronic data output from the pixels of the image input means isseparated into a brightness component and a color difference componentwhen image processing is performed. To detect an edge as describedabove, the brightness component separated from the electronic data isused.

To use the brightness component to detect an edge, if the image is animage with large change in brightness component for each pixel like animage of photographing a landscape or a portrait, for example, an edgecan be detected effectively.

However, for an image with small brightness change, but with large huechange like an image of photographing a picture pattern printed onclothing, for example, if the brightness component is used for detectingan edge, it is feared that the edge which should be actually containedin the image may not be detected.

That is, in the image processing method in the related art using onlythe brightness component, if an edge of the brightness component is notcontained in and an edge of the color difference component is containedin the pixel of interest, no edge may be detected. Consequently,smoothing is also performed in the surroundings of the edge and there isa fear of incurring breaking of the image.

The number of pixels of the electronic data output from the image inputmeans depends on the number of pixels of the image input means. Thus, toform an image having a larger number of pixels than that of theelectronic data output from the image input means, pixels need to beinterpolated.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an imageprocessing method, an image processing program, an image processingapparatus, and a digital still camera using the image processingapparatus for improving the edge detection accuracy regardless of thetype of image.

In the image processing method, the image processing program, or theimage processing apparatus of the invention, electronic data isseparated into a brightness component and a color difference componentand the edge amount is calculated for each of the provided brightnesscomponent and color difference component. The component having themaximum edge amount is selected from the calculated edge amounts,namely, the brightness component edge amount and the color differencecomponent edge amount, and the selected component is of the maximum edgeamount. The edge information about the selected component of the maximumedge amount is calculated and the electronic data is processed based onthe edge information. The edge information is, for example, the edgemagnitude, namely, the output value change amount of the electronic dataand the edge direction, namely, the output value changing direction ofthe electronic data.

The component having the maximum edge amount is selected from thebrightness component edge amount and the color difference component edgeamount, whereby in the color space of Y (brightness), Cb (colordifference 1), and Cr (color difference 2), for example, the edge of thecolor difference component Cb or Cr having the larger edge amount can bedetected even when the change amount of the brightness component Y issmall. Thus, if the edge of the brightness component cannot be detected,the edge of the color difference component can be detected and the edgedetection accuracy can be improved. Therefore, the edge detectionaccuracy can be improved regardless of the type of image.

In the image processing method, the image processing program, or theimage processing apparatus of the invention, a set of data each havingR, G, and B color components are obtained, and the edge amount may becalculated for each of the provided color components. The colorcomponent having the maximum edge amount is selected from the calculatededge amounts, namely, the color component edge amounts, and the selectedcomponent is of the maximum edge amount. The edge information about theselected component of the maximum edge amount is calculated and theelectronic data is processed based on the edge information.

The color component having the maximum edge amount is selected fromamong the color components, whereby in the color space of the primarycolors of R (red), G (green), and B (blue), for example, even when thechange amount of the R component is small, the edge of any other colorcomponent G or B having the larger edge amount can be detected. Thus, ifthe edge of one color component cannot be detected, the edge of anyother color component can be detected and the edge detection accuracycan be improved. Therefore, the edge detection accuracy can be improvedregardless of the type of image.

Further, in the image processing method or the image processing programof the invention, the maximum edge amount is selected and the edgeinformation is calculated for each pixel. Thus, the edge contained in animage can be detected in pixel units. Therefore, the edge detectionaccuracy can be improved and the image processing accuracy can beenhanced.

Further, the image processing of the invention is applied to a digitalcamera, whereby the image processing accuracy can be enhanced and afiner image can be provided.

Features and advantages of the invention will be evident from thefollowing detailed description of the preferred embodiments described inconjunction with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a flowchart to show a flow of an image processing method usinga digital camera according to one embodiment of the invention;

FIG. 2 is a block diagram to show the digital camera according to theembodiment of the invention;

FIG. 3 is a block diagram to show details of a processing circuit of thedigital camera according to the embodiment of the invention;

FIG. 4 is a schematic drawing to show CCD of the digital cameraaccording to the embodiment of the invention;

FIGS. 5A and 5B are schematic representations to show a Prewittoperator, FIG. 5A is a schematic representation to show edge detectionin an X direction and FIG. 5B is a schematic representation to show edgedetection in a Y direction;

FIG. 6 is a drawing to describe the relationship between the edge andthe edge gradient about the pixel of interest in the image processingmethod according to the embodiment of the invention; and

FIG. 7 is a drawing to describe the smoothing range about the pixel ofinterest in the image processing method according to the embodiment ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the accompanying drawings, there is shown a preferredembodiment of the invention.

FIG. 2 shows a digital camera 1 incorporating an image processingapparatus according to one embodiment of the invention.

As shown in FIG. 2, the digital camera 1 is made up of a control section10, image input means 20, a record section 30, a display section 40, aninterface 50, and the like.

The control section 10 is electric circuitry for processing electronicdata output from the image input means 20. It has a CPU (CentralProcessing Unit) 11, ROM (Read-Only Memory) 12, and a processing circuit60. The ROM 12 records a computer program executed by the CPU 11 and theprocessing circuit 60 of the control section 10.

As shown in FIG. 3, the processing circuit 60 is made up of edgeinformation calculation means 61, filter information selection means 62,smoothing processing means 63 as image processing means, and write means64 as record means.

As shown in FIG. 2, input means for accepting entry from the user isconnected to the control section 10. The input means includes a shutterbutton 71 for the user to enter an execution command of photographing, aplurality of input buttons 72 for the user to operate various functionsof the digital camera 1, and the like.

The image input means 20 has a condensing lens 21, CCD 22, and an A/Dconverter 23. The condensing lens 21 gathers light from a subject on theCCD 22. The CCD 22 has a plurality of image pickup devices arranged likea matrix in horizontal and vertical directions, and one image pickupdevice forms one pixel.

Color filters are placed on the light reception side of the image pickupdevices. As the color filters, complementary color filters made up of Cy(Cyan), Mg (Magenta), Ye (Yellow), and G (Green) are used. Thecomplementary color filters of the CCD are placed, for example, as shownin FIG. 4. Each color filter transmits light of the colors of the threeprimary colors of light as follows: Cy=G+B, Mg=B+R, and Ye=G+R. That is,one filter allows light of two colors to pass through.

Light incident on each image pickup device of the CCD 22 is convertedinto an electric signal for output. The electric signal output from theCCD 22 is an analog signal and thus is converted into digital electronicdata by the A/D converter 23.

The record section 30 has RAM (Random Access Memory) 31 and flash memory32. DRAM (Dynamic RAM) having a self-refresh function is used as the RAM31. The flash memory 32 is a rewritable record medium capable ofretaining the record contents if it is not energized, and is containedin the digital camera 1 or is detachably attached to the digital camera1.

The RAM 31 temporarily records digital electronic data processed by thecontrol section 10 or output from the A/D converter 23. The flash memory32 stores the electronic data temporarily recorded in the RAM 31. Filterinformation described later is also recorded in the flash memory 32.

The display section 40 has a liquid crystal display (LCD) 41 and VRAM(Video RAM) 42. The LCD 41 displays an image based on the electronicdata recorded in the flash memory 32 or the digital electronic dataoutput from the A/D converter 23. Display data prepared from electronicdata for display on the LCD 41 is recorded in the VRAM 42.

The interface 50 outputs the electronic data recorded in the flashmemory 32 to an external machine, such as a personal computer.

Next, processing of the control section 10 will be discussed in detail.

The control section 10 comprises the processing circuit 60 as describedabove. The processing circuit 60 is a dedicated arithmetic unit forexecuting image processing. The processing circuit 60 executespredetermined processing by a computer program recorded in the ROM 12.In the embodiment, smoothing processing for removing noise contained inelectronic data will be discussed as an example of image processing.

Processing executed by each means of the processing circuit 60 and aflow of the processing will be discussed with reference to FIGS. 1 and3. The processing executed by each means of the processing circuit 60 isperformed as pipeline processing without using the CPU 11.

(Edge Information Calculation Means)

The edge information calculation means 61 executes edge extractionprocessing from the electronic data of an image output from the imageinput means. It calculates the edge amount from the extracted edge.

The edge extraction processing is executed based on the electronic dataoutput for each pixel of the CCD 22. The electronic data output fromeach pixel contains a brightness component and a color differencecomponent and thus is separated into a brightness component and a colordifference component before the edge extraction processing is executed(S100). In the embodiment, an example wherein YCbCr color space ofbrightness component Y and color difference components Cb and Cr is usedwill be discussed.

With the CCD 22 having the color filters of four colors as shown in FIG.4, the brightness component Y and the color difference components Cb andCr are calculated from output values of electronic data output from fourpixels contiguous with the pixel of interest.

Edge extraction processing is executed for each component from thebrightness component Y and the color difference components Cb and Crcalculated (S200). As a method of the edge extraction processing, aPrewitt operator to find the differentiation value of pixel is used. ThePrewitt operator is indicated by the following expression: (The pixel ofinterest is P (i, j) as shown in FIG. 5.)

Δ fx = {P(i + 1, j − 1) − P(i − 1, j − 1)} + {P(i + 1, j) − P(i − 1, j)} + {P(i + 1, j + 1) − P(i − 1, j + 1)}Δ fy = {P(i − 1, j − 1) − P(i − 1, j + 1)} + {P(i, j − 1) − P(i, j + 1)} + {P(i + 1, j − 1) − P(i + 1, j + 1)}

In the expression, edge extraction is performed based on the electronicdata output from the pixels in the proximity of the pixel of interest Pas shown in FIG. 5, the pixels making up a 3×3 matrix 80 centering onthe pixel of interest P in the embodiment. In the edge extraction, theedge components in the arrow X direction and the arrow Y direction inFIG. 5 are detected. Output from the pixels as the electronic data is256-step gradation data of 0 to 255, for example, if output is eight-bitdata.

Next, from the extracted edges in the above-mentioned expression, theedge gradient magnitude, namely, the edge amount is calculated for eachof the brightness component Y and the color difference components Cb andCr (S300). The edge amount G is calculated according to the followingexpression (A):

[Expression 1]

$\begin{matrix}{{G(\varphi)} = \sqrt{{\Delta\; f_{x}^{2}} + {\Delta\; f_{y}^{2}}}} & (A)\end{matrix}$

The edge amount may be calculated according to the following expression(A1) or (A2) in place of the expression (A): (Expression (A1) or (A2)makes it possible to find the edge amount at higher speed.)

[Expression 2]G(φ)=|Δf _(x) |+αf _(y)  (A1)

[Expression 3]G(φ)=max(Δf _(x) ,Δf _(y))  (A2)

The edge refers to a portion where the gradation of the electronic dataoutput from pixel changes largely, namely, the boundary portion betweenobjects contained in the image. On both sides of the edge, the gradationof the electronic data output from pixel changes largely.

The edge information calculation means 61 calculates the edge amount Gfor each pixel of the CCD 22 based on the expression (A). The edgeamount is calculated for each of the brightness component Y and thecolor difference components Cb and Cr as described above.

The edge amounts calculated for the brightness component Y and the colordifference components Cb and Cr are Gy, Gcb, and Gcr respectively. Whencalculating the edge amounts Gy, Gcb, and Gcr, the edge informationcalculation means 61 selects the component having the largest edgeamount, namely, maximum edge amount Gmax from among the edge amounts Gy,Gcb, and Gcr calculated about the pixel of interest (S400). In theembodiment, as an example, the color difference component Cb is thecomponent having the maximum edge amount Gmax, namely, the selectedcomponent.

When the component having the maximum edge amount Gmax is selected, edgeinformation is calculated for the component (S500). The edge informationis information consisting of the edge amount G and edge gradientdirection θg. Therefore, when the edge information calculation means 61selects the color difference component Cb as the component having themaximum edge amount Gmax, then it calculates the edge information aboutthe color difference component Cb. The edge gradient direction θg iscalculated according to the following expression (B):

[Expression 4]

$\begin{matrix}{\theta_{g} = {\tan^{- 1}\left( \frac{\Delta\; f_{y}}{\;{\Delta\; f_{x}}} \right)}} & (B)\end{matrix}$

The edge gradient direction θg is the direction in which change in thegradation of the electronic data occurs. Therefore, the direction ofedge E and the edge gradient direction θg have vertical relationship asshown in FIG. 6.

(Filter Information Selection Means)

When the edge information calculation means 61 calculates the edgeinformation consisting of the maximum edge amount Gmax and the edgegradient direction θg for each pixel of the CCD 22, the filterinformation selection means 62 selects filter information recorded inthe flash memory 32. The filter information selection means 62 selectsthe filter information corresponding to the calculated maximum edgeamount Gmax and edge gradient direction θg and the smoothing strengthfrom among a plurality of pieces of filter information recorded in theflash memory 32 (S600).

The filter information is provided by deforming a smoothing filter setbased on a Gaussian distribution based on the above-mentioned edgeinformation. Here, the principle will be discussed using an example. Inthe embodiment, a 5×5 matrix M centering on the pixel of interest P isthe smoothing range, as shown in FIG. 7.

Not only the edge information, but also the smoothing strength iscalculated from the electronic data output from the image input means20. Based on the electronic data output from each pixel of the CCD 22,the smoothing strength is calculated for the component corresponding tothe maximum edge amount Gmax selected by the edge informationcalculation means 61. The smoothing strength σ is calculated accordingto the following expression (C). The output value of the componentcorresponding to the maximum edge amount Gmax in the electronic data,namely, the color difference component Cb in the embodiment is M.

[Expression 5]

$\begin{matrix}{\sigma = {{N(M)} = {\left( \frac{\mathbb{e}M}{n} \right)^{2}{\exp\left( {- \frac{2M}{n}} \right)}}}} & (C)\end{matrix}$

In expression (C), e is a natural logarithm and n is the brightness atwhich noise reaches the maximum. n changes with the photographingcondition; for example, in the embodiment wherein output from each pixelis an eight-bit 256-step gradation, n is set to 50 (n=50).

The smoothing range is calculated from the smoothing strength σcalculated according to the expression (C). The smoothing range is foundbased on the Gaussian distribution described later.

The filter information is provided by deforming the smoothing filter setbased on the Gaussian distribution based on the above-mentioned edgeinformation.

The Gaussian distribution is found according to the following expression(D):

[Expression 6]

$\begin{matrix}{{\delta\left( {x,y} \right)} = {\frac{1}{2{\pi\sigma}^{2}}{\exp\left( \frac{{n^{2}\left( {{x\;\cos\;\theta_{g}} - {y\;\sin\;\theta_{g}}} \right)}^{2} + {m^{2}\left( {{x\;\sin\;\theta_{g}} + {y\;\cos\;\theta_{g}}} \right)}^{2}}{{- 2}\sigma^{2}} \right)}}} & (D)\end{matrix}$

Expression (D) is deformation of a Gaussian distribution expression; itis deformed to an ellipse scaled to 1/n in the minor axis direction and1/m in the major axis direction and is rotated clockwise by θg. That is,the shape of the ellipse is changed in accordance with m and n and thegradient of the ellipse is changed in accordance with θg. m and n arescaling parameters and depend on the maximum edge amount Gmax of theedge amounts calculated according to the above-described expression (A).

As the maximum edge amount Gmax grows, the values of the scalingparameter m and n (mainly, the value of n) are increased for deformingthe ellipse to a flat elliptical shape. As shown in FIG. 7, thesmoothing range along the edge E is found by rotating in response to thegradient direction θg. That is, when the values of the scaling parameterm and n are small, smoothing range A1 is circular as indicated by thedashed line in FIG. 7; as the values of the scaling parameter m and n(particularly, the value of n) grow, a smoothing range A2 becomes a flatelliptical shape as indicated by the solid line in FIG. 7.

When the edge amount is small as a result of calculating the edgeinformation about the pixel of interest P, the periphery of the pixel ofinterest is a flat part. Therefore, the electronic data output from thepixel of interest P needs to be distributed evenly to the pixelssurrounding the pixel of interest P. Thus, the smoothing range becomes acircular range centering on the pixel of interest P.

On the other hand, when the edge amount is large, the periphery of thepixel of interest is an edge part. Therefore, the electronic data outputfrom the pixel of interest P needs to be distributed to the pixels alongthe edge surrounding the pixel of interest P. Thus, the smoothing rangebecomes an elliptical range along the edge E centering on the pixel ofinterest P. That is, as the edge gradient grows, smoothing processingalong the edge E needs to be executed increasingly.

The filter information set as described above is previously preparedcorresponding to the maximum edge amount Gmax, the edge gradientdirection θg, and the smoothing strength σ calculated and is recorded inthe flash memory 32. Therefore, the filter information selection means62 selects the optimum filter information out of the flash memory 32based on the maximum edge amount Gmax, the edge gradient direction θg,and the smoothing strength σ calculated. Therefore, the filterinformation can be provided at high speed as compared with the casewhere the filter information is calculated each time.

(Smoothing Means)

When the filter information selection means 62 selects the filterinformation, the smoothing processing means 63 executes smoothingprocessing from the electronic data output from the pixel of interest Pand the selected filter information (S700). That is, processing of theoutput electronic data is executed. The smoothing processing is executedby multiplying the raw data of the electronic data output from the pixelof interest P by the numeric value of the filter information.

As described above, the filter information selection means 62 selectsthe filter information based on the maximum edge amount Gmax, the edgegradient direction θg, and the smoothing strength σ calculated from theoutput values of the pixels making up the matrix surrounding the pixelof interest. The raw data of the electronic data output from the pixelof interest P is multiplied by the filter information, whereby theinformation of the pixel of interest P is distributed to specific pixelsof the 5×5 matrix M centering on the pixel of interest P. As theinformation of the pixel of interest P is distributed to specific pixelsof the matrix M, the smoothing processing is performed for theelectronic data of the pixel of interest P.

The smoothing processing is performed for all pixels making up an image,namely, all pixels of the CCD 22. For one pixel, the smoothingprocessing is performed in 24 pixels surrounding that pixel and thus isexecuted 25 times per pixel. The sum total of the smoothing processingexecuted for the surrounding pixels becomes the electronic dataresulting from the smoothing processing.

(Write Means)

Upon completion of the smoothing processing by the smoothing processingmeans 63, the write means 64 writes the complete electronic data intothe RAM 31 (S800).

When the write means 64 writes the one-pixel electronic data into theRAM 31, the electronic data stored in the RAM 31 is compressed to reducethe amount of data recorded in the flash memory 32. For the image pickedup with the digital camera 1, a file format such as JPEG (JointPhotographic Experts Group) or TIFF 20 (Tagged Image File Format) isused as the compression format. The compressed electronic data isrecorded in the flash memory 32.

Next, the operation of the digital camera 1 of the embodiment will bediscussed.

(1) If a power switch (not shown) of the digital camera 1 is set to ON,the digital camera enters a standby state in which it can photograph atany time. At this time, in the CCD 22, light gathered through thecondensing lens 21 is converted into an electric signal every fractionof a second to every few hundredths of a second. The provided electricsignal is converted into digital electronic data by the A/D converter23. For the user to use the LCD 41 as a finder, the digital electronicdata output from the A/D converter 23 is transferred to the VRAM 42 andthe photograph subject is displayed as a moving image on the LCD 41.

(2) When a “semi-press” state in which the user presses the shutterbutton to the midpoint of the operation range is entered, light exposureand focus are set and fixed. The light exposure at the photographingtime can be changed as the CPU 11 of the control section 10 controls theaperture of the condensing lens 21 and the shutter speed, namely, thecharge storage time of the CCD 22. As the shutter of the digital camera1, either or both of a mechanical shutter for physically shielding lightor an electronic shutter for controlling the charge storage time of theCCD 22 is used.

(3) When a “full-press” state in which the user presses the shutterbutton to the limit of the operation range is entered, the followingprocessing is performed. First, precise light measurement, focusing, andthe like are performed for the subject. Upon completion of the lightmeasurement and focusing, all charges stored in the CCD 22 are oncedischarged and then light from the subject is incident on the CCD 22through the condensing lens 41 and the CCD 22 outputs an electric signalbased on the amount of charges responsive to the amount of the incidentlight.

(4) The electric signal output from the CCD 22 is converted into digitalelectronic data by the A/D converter 23. To speed up, the digitalelectronic data is temporarily stored in the RAM 31 directly with theaddress thereof specified not via the CPU 11 of the control section 10by DMA (Direct Memory Access).

(5) The electronic data stored in the RAM 31 is subjected to theabove-described processing by the processing circuit 60 and then isgenerated as the electronic data of the appropriate color image. Toincrease the number of records in the flash memory 32, the electronicdata is compressed to the electronic data in a file format such as JPEG.

(6) Upon completion of compressing the electronic data, the electronicdata is copied into and recorded in the flash memory 32 from the RAM 31.

As described above, according to the image processing method using thedigital camera 1 of the embodiment, the edge amounts are calculated fromthe brightness component Y and the color difference components Cb and Crseparated from the electronic data. Using the component having themaximum edge amount calculated, the edge gradient direction θg and thesmoothing strength σ are calculated. Thus, for example, even for animage whose edge cannot be detected based on the brightness component Ybecause the change amount of the brightness component Y is small, anedge can be detected based on other components. Therefore, the edgedetection accuracy is improved and the image can be smoothed based onthe detected edge information and noise contained in the image can beremoved.

In the embodiment, the filter selection means 62 selects the filterinformation based on the edge amount G, the edge gradient direction θg,and the smoothing strength σ calculated by the edge informationcalculation means 61. The filter information is previously prepared inresponse to the edge amount G, the edge gradient direction θg, and thesmoothing strength σ and is recorded in the flash memory 32. Thus, whenthe edge amount G, the edge gradient direction θg, and the smoothingstrength σ are calculated, immediately the filter information isselected out of the flash memory 32. Consequently, even if the CPU 11having a low processing capability is used, the filter information canbe provided at high speed as compared with the case where the filterinformation is created one by one. Therefore, the time required forimage processing can be shortened.

In the embodiment of the invention, the example wherein the YCbCr colorspace is used as the color space has been described, but RGB color spaceor absolute color space of Lab can also be used. Although the Prewittoperator is used as the edge detection operator, any other operationsuch as a Sobel operator may be used.

Further, in the embodiment of the invention, the smoothing processingfor removing noise contained in the electronic data has been describedas an example of the image processing. However, the invention can beapplied not only to the smoothing processing, but also to imageprocessing of detecting an edge and interpolating pixels based on thedetected edge, for example.

The invention is not limited at all to the description of the mode forcarrying out the invention and the description of the embodiments. Theinvention includes various modifications that can be conceived easily bythose skilled in the art, without departing from the description of thescope of claim.

1. An image processing method for processing electronic data of an input image, comprising: a signal separation step of separating the electronic data into a brightness component and a color difference component; an edge amount calculation step of calculating the brightness component edge amount and the color difference component edge amount for each of the brightness component and the color difference component provided at said signal separation step; a maximum edge amount selection step of selecting the maximum edge amount from among the brightness component and the color difference component calculated at said edge amount calculation step; an edge information calculation step of calculating edge information of the component corresponding to the maximum edge amount based on the maximum edge amount selected at said maximum edge amount selection step; and an electronic data processing step of processing the electronic data based on filter information that has an elliptical shape, the filter information based on the edge information calculated at said edge information calculation step; wherein the major axis of the elliptical shape is based upon the edge of the electronic data indicated by said edge information calculation step.
 2. An image processing method as claimed in claim 1, wherein at said maximum edge amount selection step and said edge information calculation step, the maximum edge amount is selected and the edge information of the component corresponding to the maximum edge amount is calculated for each of pixels of the input image.
 3. A computer-readable recording medium storing a computer program that causes a computer to execute the method according to claim 1 is recorded.
 4. A computer-readable recording medium storing a computer program that causes a computer to execute the method according to claim 2 is recorded.
 5. An image processing apparatus comprising: image input means, to which image information is input, being capable of outputting the image information as electronic data; edge information calculation means for detecting a brightness component and a color difference component from the electronic data output from said image input means and calculating edge information about the component having the maximum edge amount, of the brightness component and the color difference component; image processing means for processing the electronic data based on filter information that has an elliptical shape, the filter information based on the edge information calculated by said edge information calculation means; and record means being capable of recording the electronic data and the filter information, wherein the major axis of the elliptical shape is based upon the edge of the electronic data indicated by said edge information calculation step.
 6. An image processing apparatus as claimed in claim 5, further comprising filter information selection means for selecting the filter information to process the electronic data based on the edge information calculated by said edge information calculation means.
 7. A digital still camera comprising an image processing apparatus as claimed in claim
 5. 8. A digital still camera comprising an image processing apparatus as claimed in claim
 6. 9. An image processing method as claimed in claim 1, wherein the filter information includes an edge gradient direction that is parallel to the direction of the minor axis of the elliptical shape.
 10. A computer-readable recording medium storing a computer program that causes a computer to execute the method according to claim 9 is recorded.
 11. An image processing apparatus as claimed in claim 5, wherein the filter information includes an edge gradient direction that is parallel to the direction of the minor axis of the elliptical shape.
 12. A digital still camera comprising an image processing apparatus as claimed in claim
 11. 